Demonstrative pronouns points to the noun for which they are used. This, that, these, those, such, one, same and so are used as demonstrative Pronoun.
(1). This is indicator what is the near the speaker .e.g.
This is the what I bought yesterday.
These are that why which are less expensive.
(2). That, those indicate what is removed from the speaker.
That is Mr Sharma house.
My view are different from those of your father.
(3). Such means ‘of this kind’ or ‘of that kind’.
e.g. King are constituted such by law. ( such=king)
If RAM is a friend, show him such. (as a friend)
(4.) so: I shall give you only 100 rupees or so.
we should make people our friends and keep them so (friends)
(5) the same; you sing a song last night. Sing the same to me(the same =the song)
I got your parcel and thank you for the same.
My trouble is the same as yours.
(6). one, ones ,none
One :- when the antecedent noun is in the singular number we use one.
Your shirt is red; mine is a white one.( a shirt)
This is an easy sum ;but that is a hard one (a sum )
Ones: When the antecedent noun is in the plural number we use ones.
e.g. There are 10 poor boys and 15 reach ones. (boys).
None:- none is a shortened form of ‘not one’ but none is used for the singular as well as plural number.